Post-implantation, recipients of intracochlear implants exhibit considerable variation in speech perception performance. Such variability may have many reasons —one explanation is a non-homogeneous spatial distribution of residual VIIIth nerve fibers or of the interface between nerve fibers and electrodes. When comparing different stimulation sites within the cochlear during speech processor fitting, patients sometimes report differences in sound quality. Deactivation of those electrodes with minor quality or distorted sound perception often improves general sound sensation and speech understanding. Furthermore it has been reported that selecting different electrode groups for Continuous Interleaved Sampling (CIS) stimulation has significant influence on speech perception in a number of subjects (Wilson B S, Finley C C, Lawson D T, et al. Design and evaluation of a continuous interleaved sampling (CIS) processing strategy for multichannel cochlear implants. J Rehabil Res Dev 1993; 30:110-116.)
At present, the process for selecting which electrodes should be utilised requires eliciting comments from the patient as to whether or not the benefit of the prosthesis is improved or decreased upon making an adjustment to the electrodes being used for stimulation. There are a number of problems associated with this prior art approach. For example the adjustment is not made according to any quantitative parameter but rather is based on the somewhat subjective judgements/reactions of the patient Furthermore some patients, for example young children, may not be able to readily indicate an improvement or decrease in the quality of their hearing perception during the adjustment process. Yet a further problem is that the present approach does not readily lend itself to automation, relying as it does on trial and error, and the conscious feedback of the patient.
It is an object of the present invention to provide a method, capable of automatic operation, for selecting good and poor electrodes and for utilising this information to select electrodes for stimulation.